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/*! \internal \file
 * \brief
 * Implements gmx::DirectoryEnumerator.
 *
 * \author Erik Lindahl (original C implementation)
 * \author Teemu Murtola <teemu.murtola@gmail.com> (C++ wrapper + errno handling)
 * \ingroup module_utility
 */
#include "gmxpre.h"

#include "directoryenumerator.h"

#include "config.h"

#include <cerrno>
#include <cstdio>

#include <algorithm>
#include <string>
#include <vector>

#if HAVE_DIRENT_H
#    include <dirent.h>
#endif
#if GMX_NATIVE_WINDOWS
#    include <io.h>
#endif

#include "gromacs/utility/exceptions.h"
#include "gromacs/utility/fatalerror.h"
#include "gromacs/utility/futil.h"
#include "gromacs/utility/gmxassert.h"
#include "gromacs/utility/smalloc.h"
#include "gromacs/utility/stringutil.h"

namespace gmx
{

/********************************************************************
 * DirectoryEnumerator::Impl
 */

// TODO: Consider whether checking the return value of closing would be useful,
// and what could we do if it fails?
#if GMX_NATIVE_WINDOWS
// TODO: Consider if Windows provides more error details through other APIs.
class DirectoryEnumerator::Impl
{
public:
    static Impl* init(const char* dirname, bool bThrow)
    {
        std::string tmpname(dirname);
        // Remove possible trailing directory separator.
        // TODO: Use a method in gmx::Path instead.
        if (tmpname.back() == '/' || tmpname.back() == '\\')
        {
            tmpname.pop_back();
        }

        // Add wildcard.
        tmpname.append("/*");

        errno = 0;
        _finddata_t finddata;
        intptr_t    handle = _findfirst(tmpname.c_str(), &finddata);
        if (handle < 0L)
        {
            if (errno != ENOENT && bThrow)
            {
                const int         code = errno;
                const std::string message =
                        formatString("Failed to list files in directory '%s'", dirname);
                GMX_THROW_WITH_ERRNO(FileIOError(message), "_findfirst", code);
            }
            return NULL;
        }
        return new Impl(handle, finddata);
    }
    Impl(intptr_t handle, _finddata_t finddata) :
        windows_handle(handle),
        finddata(finddata),
        bFirst_(true)
    {
    }
    ~Impl() { _findclose(windows_handle); }

    bool nextFile(std::string* filename)
    {
        if (bFirst_)
        {
            *filename = finddata.name;
            bFirst_   = false;
            return true;
        }
        else
        {
            errno = 0;
            if (_findnext(windows_handle, &finddata) != 0)
            {
                if (errno == 0 || errno == ENOENT)
                {
                    filename->clear();
                    return false;
                }
                else
                {
                    GMX_THROW_WITH_ERRNO(FileIOError("Failed to list files in a directory"),
                                         "_findnext", errno);
                }
            }
            *filename = finddata.name;
            return true;
        }
    }

private:
    intptr_t    windows_handle;
    _finddata_t finddata;
    bool        bFirst_;
};
#elif HAVE_DIRENT_H
class DirectoryEnumerator::Impl
{
public:
    static Impl* init(const char* dirname, bool bThrow)
    {
        errno       = 0;
        DIR* handle = opendir(dirname);
        if (handle == nullptr)
        {
            if (bThrow)
            {
                const int         code = errno;
                const std::string message =
                        formatString("Failed to list files in directory '%s'", dirname);
                GMX_THROW_WITH_ERRNO(FileIOError(message), "opendir", code);
            }
            return nullptr;
        }
        return new Impl(handle);
    }
    explicit Impl(DIR* handle) : dirent_handle(handle) {}
    ~Impl() { closedir(dirent_handle); }

    bool nextFile(std::string* filename)
    {
        errno     = 0;
        dirent* p = readdir(dirent_handle);
        if (p == nullptr)
        {
            if (errno == 0)
            {
                // All the files have been found.
                filename->clear();
                return false;
            }
            else
            {
                GMX_THROW_WITH_ERRNO(FileIOError("Failed to list files in a directory"), "readdir", errno);
            }
        }
        *filename = p->d_name;
        return true;
    }

private:
    DIR* dirent_handle;
};
#else
class DirectoryEnumerator::Impl
{
public:
    static Impl* init(const char* /*dirname*/, bool /*bThrow*/)
    {
        std::string message(
                "Source compiled without POSIX dirent or Windows support "
                "- cannot scan directories. In the very unlikely event "
                "this is not a compile-time mistake you could consider "
                "implementing support for your platform in "
                "directoryenumerator.cpp, but contact the developers "
                "to make sure it's really necessary!");
        GMX_THROW(NotImplementedError(message));
    }

    bool nextFile(std::string* /*filename*/) { return false; }
};
#endif

/********************************************************************
 * DirectoryEnumerator
 */

// static
std::vector<std::string> DirectoryEnumerator::enumerateFilesWithExtension(const char* dirname,
                                                                          const char* extension,
                                                                          bool        bThrow)
{
    std::vector<std::string> result;
    DirectoryEnumerator      dir(dirname, bThrow);
    std::string              nextName;
    while (dir.nextFile(&nextName))
    {
        if (debug)
        {
            std::fprintf(debug, "dir '%s' file '%s'\n", dirname, nextName.c_str());
        }
        // TODO: What about case sensitivity?
        if (endsWith(nextName, extension))
        {
            result.push_back(nextName);
        }
    }

    std::sort(result.begin(), result.end());
    return result;
}


DirectoryEnumerator::DirectoryEnumerator(const char* dirname, bool bThrow) : impl_(nullptr)
{
    GMX_RELEASE_ASSERT(dirname != nullptr && dirname[0] != '\0',
                       "Attempted to open empty/null directory path");
    impl_.reset(Impl::init(dirname, bThrow));
}

DirectoryEnumerator::DirectoryEnumerator(const std::string& dirname, bool bThrow) : impl_(nullptr)
{
    GMX_RELEASE_ASSERT(!dirname.empty(), "Attempted to open empty/null directory path");
    impl_.reset(Impl::init(dirname.c_str(), bThrow));
}

DirectoryEnumerator::~DirectoryEnumerator() {}

bool DirectoryEnumerator::nextFile(std::string* filename)
{
    if (impl_ == nullptr)
    {
        filename->clear();
        return false;
    }
    return impl_->nextFile(filename);
}

} // namespace gmx
